[BUGFIX] Restrict composer-runtime-api to 2.1

With https://review.typo3.org/c/Packages/TYPO3.CMS/+/71075
usage of InstalledVersions class was introduced.
More specifically the install_path of the root package.

However install paths of packages are only available
in composer-runtime-api 2.1, therefore we need to
require this a minimum version.

As drive by change the usage of Composer runtime API
is encapsulated in the Environment class and
path normalisation is put there as well, to not require
normalisation for each package.

composer req composer-runtime-api:^2.1
composer req composer-runtime-api:^2.1 -d typo3/sysext/core/ --no-update

Resolves: #95237
Related: #94996
Related: #95171
Releases: master

Change-Id: Ibe8f676830327b1036be8074e0dc38e54743b479
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/71083


Tested-by: core-ci <typo3@b13.com>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>